Ranger fans who don’t want to shell out hundreds of bucks for high-priced tickets to see the Blueshirts’ quest for the Stanley Cup — or even for basic cable — are finding free-of-charge alternatives that have TV networks and professional sports leagues sweating.

It’s believed that thousands of fans watched Sunday night’s Ranger playoff game on popular pirate sports sites such as Stream2watch.me, according to Crain’s New York.

And with the emergence of the live social-media platform Periscope, it appears more and more fans are willing to put up with choppy video and erratic sound as long as it doesn’t cost them a dime, Crain’s reported.

“It’s a huge, huge concern,” said Austin Berglas, head of U.S. cyber investigations at K2 Intelligence. “I did a lot of work with Major League Baseball on this, and they lose a ton of money from piracy.”

It’s easy to see why leagues and TV providers quake at any hint of games being shown for free.

“Sports are one of the few reasons why consumers are still paying for the cable or pay-TV bundle,” Amy Yong, an analyst at Macquarie Securities, told Crain’s.

With new technologies constantly emerging, the old guard is fighting a “whack-a-mole” battle.